<slot /> used as a passthrough outlet inside an SFC template (e.g.
DialogTrigger.vue's <Primitive as-child><slot /></Primitive>) resolves
through Vue's renderSlot() helper, which always wraps the forwarded
content in a Fragment vnode -- even when there's exactly one real
child. Slot was cloning that inert Fragment wrapper instead of the
real child, so attrs merged onto asChild-forwarded elements (data-slot,
aria-*, the click handler) silently vanished. Found via manual
Storybook verification: the Dialog trigger rendered but never opened
the dialog on click.
Unwrap single-child Fragments before merging/cloning, and add a
regression test through a real SFC fixture (a raw h()-based test
doesn't reproduce this, since it never goes through renderSlot()).
